By Greg Savoy and Jarrett Renshaw PITTSBURGH/LATROBE, Pa. (Reuters) -Former President Barack Obama warned about divisions fueling a “dangerous climate” in U.S. politics as he stumped for Democratic candidates on Saturday three days ahead of midterm elections that will determine control of Congress. The biggest names in Democratic and Republican politics — Obama, President Joe Biden and his predecessor Donald Trump — are in Pennsylvania on Saturday hoping to tip the balance in a pivotal midterm U.S. Senate race between Democrat John Fetterman and Republican celebrity doctor Mehmet Oz. Speakin…